Is there also such a thing as an olfactory illusion? (part 4)

This question was posed as part of New Scientist’s Last Word series, in which readers give scientific answers to each other’s questions. Here’s what our readers had to say

21 October 2026

There are optical illusions and audio illusions. Is there also such a thing as an olfactory illusion? (continued)

Richard Reubin
Via email

Olfactory illusions or olfactory hallucinations do exist and are described in the medical literature. The phenomenon is called phantosmia and can occur randomly in otherwise well people, but it also occurs during or after chemotherapy for various cancers.

From personal experience after chemotherapy, I can vouch that the phenomenon is quite disconcerting.

The phantom smells I was aware of were often of a putrid nature, and this led me to search for sources around the house and waste bins.

Andy Croft
Portsmouth, Hampshire, UK

Some years ago, my migraine aura changed from pretty lights to a smell, one of burnt toast. According to the neurologist who confirmed it, this is something that doctors see happen more frequently than most people realise.

Ametrine Lavender
Hebden Bridge, West Yorkshire, UK

On the subject of hallucinating the smell of daffodils due to a brain tumour, as mentioned by a previous correspondent, I am reminded of a friend from several decades ago who had epilepsy.

Her reliable pre-seizure aura was the smell of lemons.

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